如何覆盖 MassTransit 默认交换和队列拓扑约定? [英] How to override MassTransit default exchange and queue topology convention?

问题描述

正如 [在我关于 SO 的一个问题中] 所指出的(为什么 MassTransit 中的简单配置会创建 2 个队列和 3 个交换?)，MassTransit for RabbitMQ 会自动创建一定数量的队列并为给定的简单配置进行交换:

As pointed out [in one of my questions on SO] (Why a simple configuration in MassTransit creates 2 queues and 3 exchanges?), MassTransit for RabbitMQ creates automatically a certain number of queues and exchange for a given simple configuration:

交换，所有扇出:

• ConsoleApp1:Program-YourMessage:耐用
• VP0003748_dotnet_bus_6n9oyyfzxhyx9ybobdmpj8qeyt:自动删除和耐用?
• test_queue:耐用

• ConsoleApp1:Program-YourMessage: Durable
• VP0003748_dotnet_bus_6n9oyyfzxhyx9ybobdmpj8qeyt: Auto-delete and Durable?
• test_queue: Durable

队列:

• VP0003748_dotnet_bus_6n9oyyfzxhyx9ybobdmpj8qeyt:x-expire 60000
• test_queue:耐用

• VP0003748_dotnet_bus_6n9oyyfzxhyx9ybobdmpj8qeyt: x-expire 60000
• test_queue: Durable

然而，我发现无法覆盖这些交换和队列的命名有点令人沮丧.有什么我可以做的改变吗?

However, I found it a bit frustration to not be able to override the naming of those exchanges and queues. Is there anything I can do to change that?

例如，如果您重构某些类型或命名空间，您最终可能会因大量不再使用的交换而污染您的 RabbitMQ 实例 =/

For example, if you refactor some type or a namespace you may endup polluting your RabbitMQ instance with tons of exchanges that are no longer used =/

我理解 test_queue 因为这是我决定的非常公平的事情.类型很容易发生变化/重构.

I understand test_queue cause this is something I decided so fair enough. Types are easily subject to changes / refactoring.

推荐答案

这是一个简单有效的方法:https://bartwullems.blogspot.com/2018/09/masstransitchange-exchange-naming.html

This is a simple and effective way to do it: https://bartwullems.blogspot.com/2018/09/masstransitchange-exchange-naming.html

但最好在此处删除一些 dotnet 核心代码，以帮助任何刚开始的人.

But better to drop some dotnet core code here, to help anyone that's starting.

我们基于配置的自定义格式化程序:

Our configuration based custom formatter:

public class BusEnvironmentNameFormatter : IEntityNameFormatter
{
    private readonly IEntityNameFormatter _original;
    private readonly string _prefix;

    public BusEnvironmentNameFormatter(IEntityNameFormatter original, SomeAppSettingsSection busSettings)
    {
        _original = original;
        _prefix = string.IsNullOrWhiteSpace(busSettings.Environment)
            ? string.Empty // no prefix
            : $"{busSettings.Environment}:"; // custom prefix
    }

    // Used to rename the exchanges
    public string FormatEntityName<T>()
    {
        var original = _original.FormatEntityName<T>();
        return Format(original);
    }

    // Use this one to rename the queue
    public string Format(string original)
    {
        return string.IsNullOrWhiteSpace(_prefix)
            ? original
            : $"{_prefix}{original}";
    }
}

然后使用它，我们会做这样的事情:

Then to use it, we would do something like this:

var busSettings = busConfigSection.Get<SomeAppSettingsSection>();
var rabbitMqSettings = rabbitMqConfigSection.Get<SomeOtherAppSettingsSection>();

services.AddMassTransit(scConfig =>
{
    scConfig.AddConsumers(consumerAssemblies);

    scConfig.AddBus(provider => Bus.Factory.CreateUsingRabbitMq(rmqConfig =>
    {
        rmqConfig.UseExtensionsLogging(provider.GetRequiredService<ILoggerFactory>());

        // Force serialization of default values: null, false, etc
        rmqConfig.ConfigureJsonSerializer(jsonSettings =>
        {
            jsonSettings.DefaultValueHandling = DefaultValueHandling.Include;
            return jsonSettings;
        });

        var nameFormatter = new BusEnvironmentNameFormatter(rmqConfig.MessageTopology.EntityNameFormatter, busSettings);
        var host = rmqConfig.Host(new Uri(rabbitMqSettings.ConnectionString), hostConfig =>
        {
            hostConfig.Username(rabbitMqSettings.Username);
            hostConfig.Password(rabbitMqSettings.Password);
        });

        // Endpoint with custom naming
        rmqConfig.ReceiveEndpoint(host, nameFormatter.Format(busSettings.Endpoint), epConfig =>
        {
            epConfig.PrefetchCount = busSettings.MessagePrefetchCount;
            epConfig.UseMessageRetry(x => x.Interval(busSettings.MessageRetryCount, busSettings.MessageRetryInterval));
            epConfig.UseInMemoryOutbox();

            //TODO: Bind messages to this queue/endpoint
            epConfig.MapMessagesToConsumers(provider, busSettings);
        });

        // Custom naming for exchanges
        rmqConfig.MessageTopology.SetEntityNameFormatter(nameFormatter);
    }));
});

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